Powder materials, methods for forming the same, and electrodes formed therefrom

Abstract

Methods are provided for forming powder materials, and the powder materials and electrodes formed therefrom are also provided. The methods include providing an initial powder having initial particles that each include an electroactive material, coating the initial particles with a doping compound that includes a dopant material to define coated particles of an intermediate powder, exposing the coated particles to a reducing agent that contains fluorine, and performing a heat treatment on the coated particles while exposed to the reducing agent at an elevated temperature and period of time sufficient to cause a solid-state reaction and diffusion of the dopant material into the electroactive material to form a doped region within the electroactive material and thereby define doped particles of a final powder material. The doped region extends at least one nanometer into the electroactive material, and the fluorine reacts with oxides formed on surfaces of the coated particles.

What is claimed is: 
     
         1 . A method, comprising:
 providing an initial powder material having initial particles that each include an electroactive material;   coating the initial particles with a doping compound that includes a dopant material to define coated particles of an intermediate powder material;   exposing the coated particles to a reducing agent; and   performing a heat treatment on the coated particles while exposed to the reducing agent at an elevated temperature and period of time sufficient to cause a solid-state reaction and diffusion of the dopant material into the electroactive material to form a doped region within the electroactive material and thereby define doped particles of a final powder material, wherein the doped region extends at least one nanometer into the electroactive material from an outermost surface thereof, wherein the reducing agent reacts with oxides formed on a surface of the coated particles during the heat treatment.   
     
     
         2 . The method of  claim 1 , wherein the electroactive material is a nickel-, manganese-, cobalt-based oxide. 
     
     
         3 . The method of  claim 1 , wherein providing the initial powder material includes:
 forming a solution of an inorganic solvent and the dopant precursor;   mixing the initial powder material into the solution to form a mixture; and   drying the mixture to obtain the coated particles of the intermediate powder material, wherein the dopant material is formed from the dopant precursor,   wherein performing the heat treatment is sufficient to form free radicals from the dopant material and facilitate the diffusion of the free radials into the lattice of the electroactive material.   
     
     
         4 . The method of  claim 3 , wherein the inorganic solvent includes dimethylformamide (DMF), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), tetrahydrofuran (THF), various esters, or acetone. 
     
     
         5 . The method of  claim 3 , wherein the solution further includes the reducing agent. 
     
     
         6 . The method of  claim 5 , wherein the reducing agent includes fluorine. 
     
     
         7 . The method of  claim 5 , wherein the reducing agent is a fluoropolymer that includes polyvinylfluoride (PVF), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), perfluoroalkoxy polymer (PFA), polychlorotrifluoroethylene (PCTFE), polyethylenetetrafluoroethylene (ETFE), or polyethylenechlorotrifluoroethylene (ECTFE). 
     
     
         8 . The method of  claim 1 , wherein exposing the coated particles of the intermediate powder material includes exposing the intermediate powder material to a gaseous mixture that includes a fluoro monomer gas and an inert carrier gas. 
     
     
         9 . The method of  claim 8 , wherein the gaseous mixture includes perfluorocycloalkene (PFCA), vinyl fluoride (fluoroethylene) (VF1), vinylidene fluoride (1,1-difluoroethylene) (VDF or VF2), tetrafluoroethylene (TFE), chlorotrifluoroethylene (CTFE), or hexafluoropropylene (HFP). 
     
     
         10 . The method of  claim 1 , wherein the initial particles of the initial powder material each include a core material that includes the electroactive material and a coating layer overlying surfaces of the core material, wherein performing the heat treatment results in the dopant material being disposed within the core material adjacent to the surfaces thereof and having a concentration of less than 30 at. % within the coating layer. 
     
     
         11 . The method of  claim 10 , wherein the reducing agent includes fluorine and the fluorine reacts with a lithium-containing compound during the heat treatment to form a passivation layer on the doped particles of the final powder material that defines an exterior surface of the doped particles. 
     
     
         12 . The method of  claim 1 , wherein each of the doped particles of the final powder material include a coating layer overlying the doped region of the electroactive material, and a passivation layer overlying the coating layer, wherein the passivation layer includes a lithium-based material. 
     
     
         13 . The method of  claim 1 , wherein the dopant material includes aluminum (Al), magnesium (Mg), titanium (Ti), gallium (Ga), zirconium (Zr), or vanadium (V), calcium (Ca), iron (Fe), chromium (Cr), molybdenum (Mo), silicon (Si), yttrium (Y), boron (B), or combinations thereof. 
     
     
         14 . The method of  claim 1 , further comprising forming an electrode that includes a layered oxide structure that includes the doped particles of the final powder material. 
     
     
         15 . A powder material including particles, each of the particles comprising:
 a core material that includes a nickel-, manganese-, cobalt-based oxide;   a doped region in the core material that extends at least one nanometer into the core material from an outermost surface thereof, wherein the doped region includes the nickel-, manganese-, cobalt-based oxide and a dopant material diffused therein, wherein the dopant material includes aluminum (Al), magnesium (Mg), titanium (Ti), gallium (Ga), zirconium (Zr), or vanadium (V), calcium (Ca), iron (Fe), chromium (Cr), molybdenum (Mo), silicon (Si), yttrium (Y), boron (B), or combinations thereof; and   a coating layer overlying the outermost surface of the core material, wherein the coating layer has a concentration of the dopant material of less than 30 at. %.   
     
     
         16 . The powder material of  claim 15 , further comprising a passivation layer overlying the coating layer that includes a lithium-based material. 
     
     
         17 . The powder material of  claim 15 , wherein the coating layer includes carbon or a carbon-based compound. 
     
     
         18 . An electrode having a layered oxide structure formed of a powder material having particles that each include a core material that includes a nickel-, manganese-, cobalt-based oxide and a coating layer overlying a surface of the core material, wherein the core material includes a dopant material disposed within a doped region of the core material adjacent to the surface thereof, wherein the dopant material includes aluminum (Al), magnesium (Mg), titanium (Ti), gallium (Ga), zirconium (Zr), or vanadium (V), calcium (Ca), iron (Fe), chromium (Cr), molybdenum (Mo), silicon (Si), yttrium (Y), boron (B), or combinations thereof, wherein the coating layer has a concentration of the dopant material of less than 30 at. %. 
     
     
         19 . The electrode of  claim 18 , further comprising a passivation layer overlying the coating layer that includes a lithium-based material. 
     
     
         20 . The electrode of  claim 18 , wherein the coating layer includes carbon or a carbon-based compound.